Lighting systems, also referred to as “illumination systems”, are known to consume a large proportion of energy in buildings and, more generally, in city infrastructures. A large part of lighting use comes in durations of high energy consumption. Lighting systems are attractive as controllable loads to enable dynamic load management because load reductions from lighting systems can be both predictable and substantial.
Lighting control systems are known where luminaires are dimmed using load-shedding ballasts by a certain amount over a duration of time. The load-shedding ballast enables the lighting system to provide cost-effective electrical demand response. U.S. Pat. No. 7,747,357 describes communication methods for transmitting and receiving load shedding messages. US patent application 2010/0117620 describes methods for automatically reducing power consumption based on load shedding requirements and set thresholds.
US2014/0139116 discloses a number of luminaires that can be communicatively coupled and networked. The luminaires may be equipped with sensors. A luminaire may autonomously adjust the luminous output responsive to an event sensed by a sensor at another luminaire in the network of luminaires.
One of the current trends in lighting systems is distributed control. In a distributed lighting control system, an intelligent luminaire has local occupancy and light sensing information and can adapt its dimming level based on either stand-alone control or in coordinated control based on exchanging limited control information with neighboring luminaires. Certain desired illumination constraints are thus met by granular adaptation of dimming levels to changing daylight and occupancy conditions. A common method for such lighting control is closed-loop feedback control. Herein, a certain set-point is specified at the light sensors in a calibration step that the controller needs to achieve. In real-time, the light sensor makes an illuminance measurement and the controller adapts the luminaire dimming level to achieve or be above the set-point. Given the distributed nature of such a lighting system, one problem relates to how dynamic load management is to be executed in such a system. Specifically, if a load shedding request comes to the building management system and is then translated to a load reduction at an area level, it would be desirable to set out how the individual luminaires should behave in order to meet the requested power reduction.
What is needed in the art is a technique for controlling lighting systems by which dynamic load management (e.g., demand response) services may be offered in a smart grid.